Unfurlable reflector



NOV. 15, 1966 CARMAN ET AL 3,286,259

UNFURLABLE REFLECTOR 2 Sheets-Sheet 1 Filed April 30, 1964 INVENTORS.FIG-2 ROBE/P7 R CAR/WAN BY EA RL ROTTMA YER ATTORNEY NOV. 15, 1966 RCARMAN ET AL 3,286,259

UNFURLABLE REFLECTOR 2 Sheets-Shet 2 Filed April 30, 1964 FIG: -3

-i ill INVENTOR5. ROBERT R CARMAN BY EARL ROTTMAYER ATTORNEY UnitedStates Patent M 3,286,259 UNFURLABLE REFLECTOR Robert R. Carman,Tallmadge, and Earl Rottmayer,

Akron, Ohio, assignors to Goodyear Aerospace Corporation, Akron, Ohio, acorporation of Delaware Filed Apr. 30, 1964, Ser. No. 363,771 8 Claims.(Cl. 343-18) This invention relates to an unfurlable reflector which maybe used to reflect solar or electromagnetic wave energy, and moreparticularly to a unique application where the reflective surfaceunfurls laterally from a central hub to an extended diameterapproximately three times the packaged diameter, and where the packagesize is small in height and compact in storage.

In many situations it is desirable to transmit signals, originating at acommon point, along parallel paths. Conversely, it may also be desirableto collect signals travelling along parallel paths and concentrate themat a common point. In order to accomplish these aims a reflector deviceis used. A parabola has the distinguishing characteristic that it willreflect all parallel impinging signals to a common focal point and isprobably the most desirable shape. Also, any signals originating at thatpoint and impinging on the reflector will leave the reflector alongparallel paths.

This type of reflector is particularly applicable to usage on spacevehicles either in combination with a solar receiver or with a radar orradio-transmitter or receiver.

In the space situation, and many other situations, it may be desired totransport the reflector, such as launching it by suitable means to itsdesired location in space. Since the reflecting parabola is rather largeand is difiicult to transport through the atmosphere in its operativecondition, it is necessary to collapse the parabola during flight or forany other transporting operation.

Various types of foldable or unfurlable parabolic reflectors for spacevehicles have been developed, but these generally have involvedutilizing a plurality of reflective surfaces folding up vertically orlongitudinally around a central extending portion from a mounting hub.An example of this type of reflector is indicated in US. Patent No.3,064,534. This type of reflector is open to the objection that thecomplicated rotation and positioning of the reflective surfaces does notachieve a true parabolic shape, and the upright positioning of theparabolic surfaces during transportation leaves them vulnerable todamage from gravitational effects or other large forces occurring duringa rocket launch. A more compact, more durable unfurlable reflector isneeded.

It is the general object of the, invention to avoid and overcome theforegoing and other difficulties of prior art practicesand meet theneeds of the art particularly with regard to an RF antenna by theprovisions of an unfurlable parabolic reflector wherein a plurality ofcurved ribs are pivotally mounted to the outer periphery of asubstantially cylindrically shaped central hub so that they can fold outlaterally like the petals of a flower to substantially increase thediameter of central hub, and with a reflective mesh screen operativelyaflixed to the ribs to form a substantially parabolically shaped dishwhen the ribs have been moved to the outwardly extended position.

A further object of the invention is to provide an unfurlable reflectorutilizing a plurality of curved ribs pivotally mounted to the outerperiphery of a cylindrically shaped hub wherein the ribs are mounted atan angle with respect to the hub so that upon lateral rotation to aninward position they stack one upon another to substantially conform toand extend the shape of the hub.

Another object of the invention is to provide an unfurlable reflectorwherein the pivotally mounted ribs are Patented Nov. 15, 1966 stackedupon each other to uniformly and solidly receive any thrust forcesoccurring during satellite launch to sub-v stantially eliminate thepossibility of damage to the reflector during satellite launch.

A further object of the invention is to provide an unfurlable reflect-orwhich may utilize a flexible electromagnetic wave reflective cloth-likematerial as the reflec tive surface or rnay use large solid formedpieces to form the reflective surface without altering the physicalconstruction of the supporting frame.

A further object of the invention is to provide an unfurlable reflectorwhich unfolds laterally from a central hub so that no complex movementsare involved, and wherein the construction is extremely simple, yethighly effective and generally reasonable in cost.

The aforesaid objects of the invention and other objects which willbecome apparent as the description proceeds are achieved 'by providingin a fold-able reflector adaptable for a space environment thecombination of a substantially cylindrically shaped hub having anelectromagnetic wave reflecting top surface, pivot means operativelymounted at equally space-d points around the circumference of said hubsubstantially adjacent to the refiective top surface thereof, aplurality of ribs each having substantially the curvature of thecircumference of the hub and being of about /2. the length thereof withone pivotally mounted to each of the pivot means, so that the pivotalplane of the ribs is in an angled relationship with respect to thereflective top surface of the hub so that the ribs stack on top of eachother when pivoted inwardly, and said ribs defining a parabolic dishshape in combina tion with the top reflective surface of the hub whenpivoted outwardly until the pivoted end thereof is substantiallyperpendicular to the circumference of the hub, rneans to pivot the ribsto the inwardly stacked position and to the outwardly parabolic dishposition, and flexible reflective means operatively affixed to the ribsand adapted to fill the spaces between adjacent ribs to define aparabolic dished reflective surface when the ribs are moved outwardly tothe parabolic dished position.

For a better understanding of the invention, reference should be had tothe accompanying drawings, 'wherein:

FIGURE 1 is a side elevational view of the foldable reflector of theinvention with the curved ribs in the outwardly extended position todefine the parabolic dished shape;

FIGURE 2 is a plan view of the reflector o-f FIGURE 1 showing therelationship of the pivotal ribs to the central hub and how thereflective mesh is attached to form the parabolic dish; a V V FIGURE 3is a side elevation partially broken away of the folda-b-le reflector ofFIGURE 1 with tJhe ribs pivoted into the stacked position and aprotective cover positioned over the central radiator to hold the ribs'in stacked position While 'fiurther illustrating in the broken awayportion the folded relation of the flexible reflective screen;

FIGURE 4 is an enlarged broken away partially sectioned elevational viewof one of the pivotal mountings for the curved ribs with the rib in thefolded position;

FIGURE 5 is an enlarged sectioned side elevation of the pivotal mountingof 'FIGURE 4 taken on the line 5-5 theneofyand FIGURE -6 is a brokenaway section of the flexible reflector screen showing the weave patterntherein to achieve the complex curvature desired.

it should be understood that the :Eoldable reflector of the inventionmay be adaptable touse on earth itself, it is particularly suited forbeing launched in conjunction with a satellite into an orbital patternin space to provide either a radar-radio or solar reflective surface asdesired, and hence it has been so illustrated and will be so described.Particularly, the description is directed to the radar radio reflectivesurface.

With reference to FIGURE 1 of the drawings, the numeral 1 indicatesgenerally a foldable reflector comprising a substantially cylindricallyshaped hub 2 pivotally mounting a plurality of curved ribs 3 at equallyspaced distances around its periphery. The ribs 3 have operativelyaffixed thereto a lightweight wire mesh 4 which describes a parabolicdish shape as defined by the ribs 3 and the hub 2. Any suitableconvenient means can be utilized to attach the wire mesh 4 to the ribs 3and the hub 2. The invention anticipates that the wire mesh 4 will bemade from a screen material in the form of I-nvar, and of a particular'orthotropic weave to allow for proper stretching during furlingoperation to conform to the parabolic shape as more fully describedhereinafter. The top surface of hub 2 is so formed to continue theparabolic dish shape of the screen 4 and forms a reflective surface asindicated by the dotted line 5. A radiating feed 6, at the focal point,is operatively mounted to the center of the hub 2 in order to providefor radar or radio radiation and reception from the reflective surfacedefined by the wire mesh 4. A support frame 7 is provided to mount thehub 2 centrally, and this may be made to telescope onto a frame 8 whichgenerally will be atfixed to a space craft 8a. Apparatus (not shown) maybe utilized to effect relative movement between the support frame 7 andthe frame 8 affixed to the space craft. Thus, the entire reflectorassembly may be moved outwardly from the space craft 8a a suflicientdistance to allow the ribs 3 to be moved to the extended position thusunturling the reflector without interference with the space craft.

FIGURE 2 provides a plan view of the relationship of the curved ribs 3to the hub 2. Note that a plurality of strengthening beams 9 support thehub 2 to a central frame 10 to which the support frame 7 may beattached. The invention contemplates that the ribs 3 will be pivota lymounted to the hub 2 at equally spaced points around the outercircumference thereof. The invention further contemplates that each rib3 shall be formed from a radius substantially equal to the radius of thehub 2, and having a length of substantially /2 the cirmumference of thehub 2. In this manner, when the ribs are moved to the outwardly orextended position, as indicated in FIGURE 2, the pivotal end issubstantially perpendicular to the circumference of the hub 2 therebyextending the diameter of the reflector to about three times thediameter of the hub 2. When the ribs 3 have come to a pre-determinedopen position and locked as indicated in FIGURE 2, the reflective wiremesh is properly stretched into a substantially true parabolic dishedshape.

As clearly seen in FIGURE 1, the parabolic dish shape as defined by thecurved ribs 3 offers a complex curvature of the wire mesh 4. Aconventionally woven Wire mesh will not :achieve this complex contour asflexible extensions in the warp and woof directions are not possible.Thus, the invention comtemplates that a wire mesh, as indicated inFIGURE 6 will be utilized. This type of wire mesh will permit alternatestretching in a vertical and a horizontal direct-ion because a pluralityof vertical connection strands, indicated generally by numeral -12alternately connect the horizontal strands indicated generally bynumeral 13. This type of rectangular weave allows in excess of 100%elongation in the warp direction with a consequent shortening in thewoof directio without yielding of the wire elements. This type ofmaterial will readily stretch one way or the other to provide the propercontours of the wire mesh 4 into the parabolic dished shape uponextension of the ribs 3.

FIGURE 3 illustrates the foldable reflector in the stacked positionwhere the ribs 3 have been pivoted inwardly towards the hub so that theytend to come into engagement with the outer surface of the hub. However,the ribs 3 are mounted at a somewhat inclined angle with relation to theplane of the hub so that they stack one upon another as clearlyindicated in FIGURE 3. Note that a protective cover 1 5 may be placedover the center of the stacked ribs 3 to protect the antenna 6, and thatarms 16 extending from the cover 15 hook over the ends of the ribs 3 tosecurely latch the stacked assembly into a fixed position. The cover 15would be aflixed to the hub 2 in a convenient manner. The night handside of FIGURE 3 is broken away to show that the reflective wire mesh 4tends to [fold inwardly into a plurality of folds indicated generally bynumeral :17 when the ribs are rotated inwardly to the stacked position.

It is an important feature of the invention that the ribs 3 be pivotallymounted to the hub 2 so that upon rotation to the outwardly extendedposition they provide a true parabolic dish shape with reference to thehub 2 as shown in FIGURE 1, when moved to the inward position theyreadily stack on top of each other as illustrated in FIGURE 3. Thispivotal mounting is shown in enlarged cross section in FIGURE 4, and isindicated generally by numeral 20. The pivotal mounting includes a pairof mounting brackets 21 and 22 operatively aflixed to the hub 2 byconvenient means such as welding, bolting or integrally formingtherewith. A rotational pin 23 is slidably received through the bottommounting plate 22 and has a smaller machined end 24 journalled in theupward support plate 21. A locking nut 25 removably screwed into thebottom support plate 22 operatively engages a lower shoulder 26 of thepin 23 to securely hold it in rotatable position between the upper andlower support plates 21 and 22. A smaller machined end 27 of the pin 23rotatably passes through the locking nut 25 and has an operating lever28 operatively secured thereto by bolt means 29. The lever means 28 isadapted to be rotatable in the horizontal plane to rotate the pin 23. Asleeve 30 is slidably received over the pin 23 and locked into positiontherewith by a key 31. One of the ribs 3 is operatively secured to thesleeve 30 by convenient means such as welding at 32. In order to insurea proper structural relationship between the rib 3 and the sleeve 30, abrace support 33 is operatively welded as at 34 therebetween. Thus,rotation of the lever 28 provides rotation of the rib 3 from the stackedposition indicated in FIGURE 3 to the extended position indicated inFIGURES 1 and 2, or vice versa. Suitable means (not shown) such aspulleys or levers attached to the hub 2 through the mounting frames 7and 8 may be utilized to actuate the lever 28. The inventioncontemplates that every pivot means 20 will be actuated simultaneouslyto move to and/or from the stacked or extended positions.

Another important feature of the invention is illustrated in FIGURE 5where it is seen that the pin 23 is actually mounted at an angle withrespect to the hub 2. This insures that the ribs 3 move downwardly intothe stacked position when they are rotated in that direction and areactually moving somewhat upwardly when rotated to the extended positionto insure the proper parabolic shape and stretching into position of thewire mesh 4. The downward movement into the stacked position furthercompresses the height of the folded package. The precise angularrelationship of the pin 23 as defined by the support flanges 21 and 22in relation to the hub 2 can vary between about one and about fifteendegrees depending upon the desired parabolic shape and the size of thereflective surface It should also be understood that the pivotalmounting of the ribs does not need to be angled as indicated in FIGURE 5in order to accomplish the objectives of the invention. However, eachrib 3 must be mounted at an upwardly directed angle with relation to thehub 2, as indicated in FIGURES 3 and 4 to insure that the ribs actuallydo stack when moved to the inward position.

While the invention has been illustrated and described as utilizing awire mesh 4 as the reflective surface for the purpose of lightening theweight and minimizing interference with solar energy, rig-id accuratelycontoured petals formed to the shape between adjacent ribs 3 in theextended position, and indicated by sections 40 in FIGURE 2, may beoperatively aflixed to each rib 3. These solid sections 40 may beadapted to slide laterally over each other when the ribs are moved tothe closed position and to form the desired parabolic shape when theribs are moved to the extended position. This type of a solid reflectivesurface would probably be most adaptable for use as the reflectivesurface for a solar reflector, but could also provide a high frequencyRF antenna. w i

Thus, it is seen that the objects, of the invention have been achievedbyproviding a foldable reflector utilizing a plurality of ribs 3pivotally mounted at equally spaced points on the outer peripheralsurface of a hub 2 so that the ribs open laterally from a stackedposition substantially extending the hub 2, as indicated in FIGURE 3, toan extended position where the pivoted ends are substantiallyperpendicular to the circumference of the hub 2 to form a parabolicdished reflective surface. The ribs 3 are pivotally mounted at an anglewith respect to the hub 2 to provide the parabolic shape and insure theywill form a stacked relationship when they are moved inwardly towardsthe hub 2. Further, the pivotal mountings may be angled so that the ribsmoved downwardly to-compress the vertical height of the reflector in thestacked position and move upwardly to insure the proper parabolic shapewhen the ribs are moved to the extended position. Generally, theinvention contemplates that Invar metal will be used for the wire meshand rib tubing to reduce any heat distortion and to increase strength ata reduced weight.

The simple mechanical structure of the apparatus utilizes no complexmovements and the stacked relationship of the ribs in the foldedposition provided a compact structure which rest-s upon itself and isadapted to receive great thrusts in the vertical direction upon launchwithout any possible structural damage. 'Ilhis design is adaptable torepeated erection and storage, launching, and any assembly orpositioning movements in space. The angled pivotal mounting of thecurved ribs 3 is designed to maintain mechanical strength and insuresurface accuracy that will provide a long efficient life time ofoperation. The utilization of the wire mesh adaptable for stretching inthe warp and woof direction insures adherence to the complex surface ofthe parabolic shape.

While in accordance with the patent statutes only one best knownembodiment of the invention has been illustrated and described indetail, it is to be particularly understood that the invention is notlimited thereto or thereby, but that the inventive scope is defined inthe appended claims.

What is claimed is:

1. In a foldable reflector adaptable for a space environment thecombination of a substantially cylindrically shaped hub having anelectromagnetic wave reflective top surface,

pivot means operatively mounted at equally spaced points around thecircumference of said hub substantially adjacent to said reflective topsurface thereof,

a plurality of ribs each having substantially the curvature of thecircumference of said hub and being of about /2 the length thereof withone rib pivotally mounted to each of said pivot means so that whenpivoted inwardly the ribs tend to come into engagement with the outersurface of said hub except that the pivotal plane of the ribs is in anangled relationship with respect to the reflective top surface of saidhub so that said ribs stack on top of each other when pivoted inwardly,and said ribs defining a parabolic dished shape in combination with saidtop reflective surface of said hub when pivoted outwardly so that thepivoted end thereof is substantially perpendicular to the circumferenceof said hub, means to pivot said ribs to the inwardly stacked pof sitionand to the outwardly parabolic dished position, and

flexible reflective means operatively affixed to said ribs and adaptedto fill the spaces between adjacent ribs to define a parabolic dishedreflective surface when said ribs are moved outwardly to the parabolicdished position.

2. In a foldable reflector adaptable for a space environment thecombination of i a substantially cylindrically shaped hub having aparabolic shaped reflective top surface,

1 pivot means operatively mounted at substantially equally spaced pointsaround the circumference of said hub substantially adjacent to saidreflective top surface thereof,

a plurality of curved ribs with one pivotally mounted at its end to eachof said pivot means adapted to pivot laterally with relation to said hubto stack on top of each other when pivoted toward said hub and define aparabolic dished shape in combination with said top reflective surfaceof said hub when w pivoted away from said hub,

means to pivot said ribs to the stacked position and to the parabolicdished position, and

flexible reflective means operatively affixed to said ribs and adaptedto fill the spaces between adjacent ribs to define a parabolic dishedreflective surface when said ribs are moved away from the hub to the vparabolic dished position.

3. In a foldable reflector adapted for a space environment thecombination of a substantially cylindrically shaped base hub having aparabolic shaped reflective top surface,

a plurality of curved radial ribs pivotally mounted at one end toequally spaced points on the circumference of said hub, said ribs havinga curvature substantially equal to the curvature of said hub andextending approximately /2 the length of the circumference thereof, sothat said ribs describe a continuation of the parabolic shapedreflective top surface of said hub when said ribs are pivoted to anextended position where the ends of said ribs are substantially normalto the circumference of said hub, and said ribs adapted to stack on topof each other when pivoted toward said hub to an inward position toessentially conform to the cylindrical shape of the hub,

means to move the ribs from the inward position to the extendedposition,

flexible wire mesh reflector means connected between each rib and saidhub adapted to be fully stretched to describe a continuation of theparabolic shaped reflective top surface of the hub when said ribs aremoved to the extended position, and

receiving means operatively mounted at the center of said hub andextending along the axis of said parabolic shape of said wire meshreflector means to lie on the focal point of said reflector means.

4. In a foldable reflector adapted for space environ ment thecombination of a substantially flat cylindrically shaped base hub havinga parabolic shaped reflective top surface,

a plurality of curved radial ribs each pivotally mounted at one end toseparate equally spaced points on the circumference of said hub so thatsaid ribs describe a parabolic shape in combination with the reflectivetop surface of said hub when said ribs are pivoted laterally away fromsaid hub to an extended position,

means to hold said ribs in a packaged position when they are movedlaterally from the extended position to lie substantially adjacent tosaid hub,

means to move the ribs to the packaged position and to the extendedposition, and

flexible wire mesh reflector means connected between adjacent ribs andsaid hub adapted to be fully stretched to describe a parabolic shapewith the reflective top surface of said hub when said ribs are moved tothe extended position.

5. A foldable reflector as set forth in claim 4 which includes thepivotal mounting of the ribs being in angled relation to thelongitudinal axis of the base hub so that the ribs move downwardly whenmoved away from said hub until the pivotal ends are substantially normalto the circumference of said hub.

6. A foldable reflector as set forth in claim 4 except that solidreflective materials are operatively secured to the ribs and adapted tofill the spaces therebetween when said ribs are moved to the extendedposition, and said solid materials are adapted to slide over each otherto form layers when said ribs are moved to the packaged position.

7. In a foldable reflector adapted for a space environment thecombination of a flat circularly shaped base hub having a parabolicshaped reflective top surface,

a plurality of curved ribs each pivotally mounted at one end to separateequally spaced points on the circumference of said h-ub so that saidribs describe a parabolic shape in combination with the reflective topsurface of said hub when said ribs are pivoted laterally away from saidhub to an extended position,

means to store said ribs in a packaged position when they are pivotedlaterally to lie adjacent said hub wherein the pivotal mounting of theribs is angled in-relation to the longitudinal axis of the hub so thatthe vertical height-of the reflector is compressed as the rib movesdownwardly when moved laterally towards said hub into the packagedposition, means to move the ribs to the packaged position and to theextended position, and

- reflector means connected between adjacent ribs and said hub adaptedto describe a parabolic shape with the reflective top surface of saidhub when said ribs are moved to the extended position.

-8: A- foldable reflector as set forth in claim 7 except that aplurality of sheets of solid reflective materials adapted to fill thespaces between adjacent ribs are provided so that a'sheet is operativelysecured to each rib so thata parabolic surface is achieved when saidribs are moved to the extended position, and said solid sheets areadapted to slide over each other in layers when said ribs are moved tothe packaged position.

References Cited by the Examiner UNITED STATES PATENTS 1,813,102 1/1931Vo'gel 240103 2,945,234 7/1960 Driscoll 343-915 3,064,534 11/1962Tumavicus 343-l8 X 3,105,486 10/1963 Glenn 8884 X 3,176,303 3/1965Holland 343915 CHESTER L. JUSTUS, Primary Examiner. G. M. FISCHER,Assistant Examiner.

1. IN A FOLDABLE REFLECTOR ADAPTABLE FOR A SPACE ENVIRONMENT THECOMBINATION OF A SUBSTANTIALLY CYLINDRICALLY SHAPED HUB HAVING ANELECTROMAGNETIC WAVE REFLECTIVE TOP SURFACE, PIVOT MEANS OPERATIVELYMOUNTED AT EQUALLY SPACED POINTS AROUND THE CIRCUMFERENCE OF SAID HUBSUBSTANTIALLY ADJACENT TO SAID REFLECTIVE TOP SURFACE THEREOF, APLURALITY OF RIBS EACH HAVING SUBSTANTIALLY CURVATURE OF THECIRCUMFERENCE OF SAID HUB AND BEING OF ABOUT 1/2 THE LENGTH THEREOF WITHONE RIB PIVOTALLY MOUNTED TO EACH OF SAID PIVOT MEANS SO THAT WHENPIVOTED INWARDLY THE RIBS TEND TO COME INTO ENGAGEMENT WITH THE OUTERSURFACE OF SAID HUB EXCEPT THAT THE PIVOTAL PLANE OF THE RIBS IS INANGLED RELATIONSHIP WITH RESPECT TO THE REFLECTIVE TOP SURFACE OF SAIDHUB SO THAT SAID RIBS STACK ON TOP OF EACH